In various schemes for interframe coding of television pictures, it is advantageous to drop or discard information from some fields or frames by subsampling the video signal at a fraction of the normal rate. This is done in order to prevent overflow of the data rate equalization buffers disposed in the transmission path, or simply to increase the efficiency of the encoder by removing redundant information. At the receiver, a reconstructed version of the information contained in the nontransmitted fields or frames is obtained by interpolation, using information derived from the transmitted fields. Simple linear interpolation may be performed by averaging the intensity information defining picture elements (pels) in the preceding and succeeding transmitted fields at fixed locations which are most closely related to the location of the picture element that is presently being processed. In certain instances, the interpolation may be performed adaptively, such that the pels used to form certain reconstructed or estimated intensity values are selected from two or more groups having different spatial patterns or such that the information obtained from pels in the same relative spatial positions in the prior and succeeding frames are combined in two or more different ways.
Both the aforementioned fixed and adaptive interpolative techniques are adequate to estimate and thus recover the nontransmitted picture information when little motion occurs in the picture. However, where objects, particularly those with a high degree of detail, are moving quickly in the field of view of the television camera, dropping fields or frames in the encoder and subsequent reconstruction using interpolation often causes blurring and other objectionable visual distortion. Accordingly, the broad object of the present invention is to enable improved estimation of intensity information defining elements in a picture using interpolative techniques on information derived from preceding and succeeding versions of the picture. A specific object is to improve the reconstruction of a nontransmitted field of a video signal using information from previous and succeeding fields, so as to eliminate annoying distortion and flicker.